Fluorescence Studies of Ligand-Induced Conformational Changes of the Na+/Glucose Cotransporter†

Biochemistry ◽  
2002 ◽  
Vol 41 (4) ◽  
pp. 1250-1258 ◽  
Author(s):  
Anne-Kristine Meinild ◽  
Bruce A. Hirayama ◽  
Ernest M. Wright ◽  
Donald D. F. Loo
Keyword(s):  
Conformational Changes ◽  
Fluorescence Studies

scholarly journals Spectroscopic studies on Tb3+ binding to S-100a protein

1987 ◽  
Vol 244 (3) ◽  
pp. 559-563 ◽  
Author(s):  
R S Mani ◽  
C M Kay
Keyword(s):  
Conformational Changes ◽  
Binding Assay ◽  
Emission Spectra ◽  
Spectroscopic Studies ◽  
Spectral Studies ◽  
Difference Spectroscopy ◽  
Fluorescence Excitation ◽  
Fluorescence Studies ◽  
Helical Content ◽  
Direct Binding

Direct binding assay and fluorescence studies revealed that S-100a protein binds 2 mol of Tb3+/mol of protein at pH 6.6. The protein binds Tb3+ much more tightly than Ca2+, and the upper limit of the observed Kd value for Tb3+ is 3.5 × 10(-6) M. The Tb3+-binding site on the protein must be close to a tyrosine residue, as indicated by fluorescence excitation and emission spectra, where energy transfer from tyrosine is noted. Addition of Tb3+ resulted in a conformational change in the protein, as revealed by u.v.-difference spectroscopy and c.d. studies. Far-u.v. c.d. studies indicated the helical content to decrease from approx. 39% to 35% in the presence of Tb3+. From u.v.-difference-spectroscopy results the single tryptophan and the tyrosine chromophores in S-100a protein are blue-shifted (i.e. exposed to the solvent) in the presence of Tb3+ and the observed conformational changes are similar to those induced by Ca2+, suggesting that Tb3+ can be employed as a Ca2+ analogue in spectral studies with S-100a protein.

Photophysical studies of hydrophobically functionalized polyionene systems in aqueous solutions

1995 ◽  
Vol 73 (11) ◽  
pp. 2041-2046 ◽  
Author(s):  
P. Uznanski ◽  
J. Pecherz ◽  
M. Kryszewski
Keyword(s):  
Energy Transfer ◽  
Conformational Changes ◽  
Hydrophobic Interaction ◽  
Polymer Chains ◽  
Anionic Dyes ◽  
Fluorescence Studies ◽  
Surfactant Aggregates ◽  
Modified Polymers ◽  
Characteristic Behaviour ◽  
Polymer Surfactant

Complexes of polyionene and anionic dyes and surfactant were prepared by exchange reaction of counterions in the parent polymer. Fluorescence studies were conducted to observe some characteristic behaviour of these complexes in water Polyionenes with aromatic hydrocarbons adopt an open conformation and there is no evidence for interpolymer interactions. On the contrary, polyionenes with long aliphatic counterions easily form microdomains in aqueous solution due to hydrophobic interaction as evidenced by an increase in excimer emission. Microdomains have an interpolymer nature, as confirmed by measurements of energy transfer from naphthalene to pyrene moieties. Polyionenes with SDS counterions interact with external surfactant molecules and form polymer–surfactant aggregates. Electrostatic repulsions between aggregates dominate on hydrophobic interaction between polymer chains and are responsible for conformational changes. Keywords: hydrophobically modified polymers, surfactants, complexation, fluorescence, nonradiative energy transfer

Fluorescence Studies on Denaturation and Stability of Recombinant Human Interferon-Gamma

2003 ◽  
Vol 58 (3-4) ◽  
pp. 288-294 ◽  
Author(s):  
Petya Christova ◽  
Kristina Todorova ◽  
Ilijana Timtcheva ◽  
Genoveva Nacheva ◽  
Andrey Karshikoff ◽  
...  
Keyword(s):  
Interferon Gamma ◽  
Conformational Changes ◽  
Electrostatic Interactions ◽  
Ph Dependence ◽  
Human Interferon ◽  
Tryptophan Residue ◽  
Substantial Impact ◽  
Fluorescence Studies ◽  
The Stability ◽  
Recombinant Human Interferon Gamma

Unfolding/folding transitions of recombinant human interferon-gamma (hIFNγ) in urea and guanidine chloride (Gn.HCl) solutions were studied by fluorescence spectroscopy. At pH 7.4 Gn.HCl was a much more efficient denaturant (midpoint of unfolding C* = 1.1 m and ΔG0 = 13.4 kJ/mol) than urea (C* = 2.8 m and ΔG0 = 11.7 kJ/mol). The close ΔG0 values indicate that the contribution of electrostatic interactions to the stability of hIFNγ is insignificant. Both the pH dependence of the fluorescence intensity and the unfolding experiments in urea at variable pH showed that hIFNγ remains native in the pH range of 4.8-9.5. Using two quenchers, iodide and acrylamide, and applying the Stern-Volmer equation, a cluster of acidic groups situated in close proximity to the single tryptophan residue was identified. Based on the denaturation experiments at different pH values and on our earlier calculations of the electrostatic interactions in hIFNγ, we assume that the protonation of Asp63 causes conformational changes having a substantial impact on the stability of hIFNγ.

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